## ΔS(universe)

$\Delta S = \frac{q_{rev}}{T}$

Janice Xiao 1I
Posts: 52
Joined: Thu Jul 13, 2017 3:00 am

### ΔS(universe)

Can ΔS(universe) decrease? If so, what does that mean?

Posts: 58
Joined: Fri Sep 29, 2017 7:06 am
Been upvoted: 1 time

### Re: ΔS(universe)

I think the entropy of the universe can only increase. I'm not sure how to explain it, but I know it can't decrease.

Yashaswi Dis 1K
Posts: 56
Joined: Fri Sep 29, 2017 7:04 am

### Re: ΔS(universe)

Hi,

So delta S according to the Second Law of Thermodynamics will always be increasing in the universe. Delta S of the system can decrease, in other words, if you freeze liquid water to ice, you are reducing the possible number of arrangements (microstates) that the H20 molecule can be in. So delta S of that system is decreasing. However, the environment around us is so large that the decrease in entropy of that system would not outweigh the delta S of the surroundings, where usually delta S increases. So that's partly why overall, the delta S in the universe is always increasing.

I would think back to the analogy that Dr. Lavelle mentioned about lighting a match outside and/or if dropping few water droplets in the ocean will really change the volume of the ocean...I think those analogies help put the Second Law of Thermodynamics into perspective.

Hope that helps!

Lourick Bustamante 1B
Posts: 50
Joined: Wed Nov 16, 2016 3:02 am

### Re: ΔS(universe)

This is a really helpful explanation! The analogy that Lavelle really helps to provide an example as to why the Second Law of Thermodynamics proves to be true. Compared to the universe, the entropy observed in a system will always be too small to have any notable effect on the universe's entropy, and in the universe, entropy is always increasing.

snehabhargava
Posts: 52
Joined: Thu Jul 13, 2017 3:00 am

### Re: ΔS(universe)

The change in entropy of the universe is the same always.

Hellen Truong 2J
Posts: 50
Joined: Sat Jul 22, 2017 3:00 am
Been upvoted: 1 time

### Re: ΔS(universe)

snehabhargava wrote:The change in entropy of the universe is the same always.

Wait how can this be true? I think my TA said that delta S can be zero for reactions at equilibrium or something like that?

Rohan Chaudhari- 1K
Posts: 32
Joined: Fri Sep 29, 2017 7:06 am

### Re: ΔS(universe)

Delta S can only be zero in an equilibrium, one way to think about that could be that disorder and order are equal. Likewise, entropy in the universe is always increasing.

### Who is online

Users browsing this forum: No registered users and 1 guest